JP5377219B2 - Magnetic resonance imaging apparatus and magnetic resonance imaging method - Google Patents

Abstract

When determined that a body-motion is produced before starting a main-imaging, a sequence-switching control-unit controls operation so as to switch from a usual-imaging sequence to a body-motion adaptive-sequence corresponding to an imaging-portion of a subject P by referring to a body-motion adaptive-sequence storage-unit. Moreover, upon a determination that a body-motion is produced during the main-imaging according to the usual-imaging sequence, the sequence-switching control-unit refers to a collected-data storage-unit, and controls operation so as to perform a retake by switching to the body-motion adaptive-sequence if an already-collected data-volume is less than a predetermined volume. By contrast, if the already-collected data-volume is equal to or more than the predetermined volume at a time point when determined that a body-motion is produced during the main-imaging according to the usual-imaging sequence, the sequence-switching control-unit stops the main-imaging, and controls a data-processing unit so as to reconstruct a magnetic resonance image only with collected data.

Description

  The present invention relates to a magnetic resonance imaging diagnostic apparatus and a magnetic resonance imaging method.

  2. Description of the Related Art Conventionally, in a magnetic resonance imaging apparatus, a subject placed on a top mat on a bed is fed into a magnet having an opening with a local imaging RF coil attached as necessary. Then, a magnetic resonance image is taken. Specifically, the magnetic resonance diagnostic imaging apparatus uses a radio frequency (RF) for a subject placed in a static magnetic field based on a predetermined data collection method (for example, Spin Echo method, Fast Spin Echo method, etc.). ) A magnetic resonance image is reconstructed by collecting magnetic resonance (MR) signals emitted from a subject by irradiation of a magnetic field and a high-frequency magnetic field.

  By the way, if the subject moves during imaging, artifacts due to the movement will occur in the magnetic resonance image. Such an artifact becomes a cause of difficulty in image diagnosis using a magnetic resonance image by a doctor. For this reason, in general, an operator of the magnetic resonance imaging diagnostic apparatus verbally tells the subject “Do not move during imaging” before imaging.

  However, if it is determined that only magnetic resonance images that cannot be diagnosed due to the movement of the subject during imaging even if imaging is started after telling the subject not to move by oral response, The operator interrupts imaging and re-images under the same conditions. In particular, when imaging a subject who is difficult to maintain a stationary state due to age or disease, the possibility of re-imaging increases.

  Therefore, in order to avoid re-imaging, a magnetic resonance image is captured by a data collection method that can correct the movement of the subject.

  For example, by using data collected by the PROPELLER (periodically rotated overlapping parallel lines with enhanced reconstruction) method, a magnetic resonance image in which the movement of the subject is corrected can be reconstructed (see, for example, Non-Patent Document 1). ).

  Here, as shown in FIG. 10, the PROPELLER method is a method of rotating k-space data in the frequency domain by repeatedly rotating a band-like region called “blade” formed by a plurality of parallel data collection trajectories for each time. It is a method of collecting and filling in a non-orthogonal shape. The PROPELLER method is also referred to as the BLADE method. Hereinafter, the PROPELLER method is simply referred to as “blade rotation data collection method”, and the pulse sequence by the “blade rotation data collection method” is referred to as “blade rotation data collection sequence”. Describe.

  In the data collected by the “blade rotation data collection sequence”, as shown in FIG. 10, data near the center of k-space (where the frequency in the phase encoding direction and the frequency encoding direction is “0”) is stored in each blade. It must exist. Therefore, by comparing the images obtained by Fourier transforming the data in the k space for each blade, it is possible to determine the amount of movement between the images corresponding to each blade having a different time series. FIG. 10 is a diagram for explaining the blade rotation data collection method.

  Then, based on the determined amount of movement, the shift between the images is corrected by relative rotational movement or translational movement, and k-space data generated by inverse Fourier transform from the image corresponding to each corrected blade is obtained. By performing Fourier transform again, it is possible to reconstruct a magnetic resonance image in which the influence of the movement is suppressed, that is, the artifact caused by the movement of the subject is suppressed.

Muro Isao et al., “Echo Train Length and Blade Number in PROPELLER Method on Motion Correction (Computer Simulation)”, Journal of Japanese Society of Radiological Technology, Vol. 60, No. 2, pp. 264-269

  By the way, in the above-described conventional “blade rotation data collection method”, the k-space data in the frequency domain is filled redundantly, so that the imaging time becomes long. In other words, if imaging is performed by the above-mentioned “blade rotation data collection method” from the beginning so that image diagnosis by a doctor is not difficult, the imaging time for each subject becomes longer, so the efficiency of image diagnosis is poor. There was a problem of becoming.

  Accordingly, the present invention has been made to solve the above-described problems of the prior art, and ensures that a magnetic resonance image in which artifacts due to the movement of the subject are suppressed is reliably captured. It is an object of the present invention to provide a magnetic resonance imaging apparatus and a magnetic resonance imaging method that can improve the efficiency of diagnosis.

  In order to solve the above-described problems and achieve the object, the present invention according to claim 1 controls to collect magnetic resonance signals from within a subject by a predetermined data collection method and to take a magnetic resonance image. When the movement of the subject is detected, the data collection method having a shorter imaging time than the predetermined data collection method or the movement of the subject can be corrected from the predetermined data collection method A data acquisition control unit that controls to collect the magnetic resonance signal by switching to the second data acquisition method, which is a data acquisition method, and a data acquisition method executed under the control of the data acquisition control unit. And an image reconstruction unit for reconstructing the magnetic resonance image from the magnetic resonance signal.

  Further, the present invention according to claim 19 controls that magnetic resonance signals from within the subject are collected by a predetermined data collection method to take a magnetic resonance image, and the movement of the subject is detected. A second data collection method that is a data collection method having a shorter imaging time than the predetermined data collection method or a data collection method capable of correcting the movement of the subject. A data acquisition control step for controlling the acquisition of the magnetic resonance signal by switching to the data acquisition method, and the magnetic resonance image from the magnetic resonance signal acquired based on the data acquisition method executed by the control of the data acquisition control step. And an image reconstruction step of reconstructing.

  According to the first or nineteenth aspect of the present invention, it is possible to ensure that a magnetic resonance image in which artifacts resulting from the movement of the subject are suppressed is reliably captured, thereby improving the efficiency of image diagnosis.

FIG. 1 is a diagram for explaining the configuration of the magnetic resonance imaging apparatus according to the present embodiment. FIG. 2 is a functional block diagram showing a detailed configuration of the computer system in this embodiment. FIG. 3 is a diagram for explaining the body motion correspondence sequence storage unit. FIG. 4 is a diagram for explaining the sequence switching control unit. FIG. 5 is a flowchart for explaining processing of the magnetic resonance imaging apparatus according to the present embodiment. FIG. 6 is a diagram (1) for explaining the fourth method. FIG. 7 is a diagram (2) for explaining the fourth method. FIG. 8 is a diagram (3) for explaining the fourth method. FIG. 9 is a diagram (4) for explaining the fourth method. FIG. 10 is a diagram for explaining the blade rotation data collection method.

  Exemplary embodiments of a magnetic resonance imaging apparatus and a magnetic resonance imaging method according to the present invention will be described below in detail with reference to the accompanying drawings. In the following, a magnetic resonance imaging apparatus for executing the magnetic resonance imaging method according to the present invention will be described as an example.

  First, the configuration of the magnetic resonance imaging apparatus in the present embodiment will be described. FIG. 1 is a diagram for explaining the configuration of the magnetic resonance imaging apparatus according to the present embodiment. As shown in FIG. 1, the magnetic resonance imaging apparatus 100 according to the present embodiment includes a static magnetic field magnet 1, a gradient magnetic field coil 2, a gradient magnetic field power supply 3, a bed 4, a bed control unit 5, and a transmission RF coil. 6, a transmission unit 7, a reception RF coil 8, a reception unit 9, and a computer system 10.

  The static magnetic field magnet 1 is a magnet formed in a hollow cylindrical shape, and is made of, for example, a magnet such as a permanent magnet or a superconducting magnet. The static magnetic field magnet 1 generates a uniform static magnetic field in the space inside the cylinder in which the subject P is arranged by a current supplied from a static magnetic field power source (not shown).

  The gradient magnetic field coil 2 is a coil formed in a hollow cylindrical shape, and is disposed inside the static magnetic field magnet 1. The gradient magnetic field coil 2 is formed by combining three coils corresponding to X, Y, and Z axes orthogonal to each other, and these three coils individually supply current from a gradient magnetic field power source 3 described later. In response, a gradient magnetic field whose magnetic field intensity changes along each of the X, Y, and Z axes is generated. The Z-axis direction is the same as the static magnetic field.

  The gradient magnetic field power source 3 is a device that supplies a current to the gradient coil 2 based on a set pulse sequence (described later) sent from the computer system 10.

  The couch 4 is a device that includes a top plate 4a on which the subject P is placed, and the couch 4a is placed on the top plate 4a under the control of the couch controller 5 described later. To insert into the cavity (imaging port) of the gradient coil 2. The bed 4 is installed such that the longitudinal direction is parallel to the central axis of the static magnetic field magnet 1.

  Moreover, as shown in FIG. 1, the pressure sensor 4b is attached to the top plate 4a, and the pressure sensor 4b detects the pressure applied to the top plate 4a. The pressure sensor 4b will be described later in detail.

  The couch controller 5 is a device that controls the movement of the couch 4 and drives the couch 4 to move the couchtop 4a in the longitudinal direction and the vertical direction.

  The transmission RF coil 6 is a coil disposed inside the gradient magnetic field coil 2 and generates a high-frequency magnetic field by a high-frequency pulse supplied from the transmission unit 7.

  The transmission unit 7 is a device that transmits a high-frequency pulse corresponding to the Larmor frequency to the transmission RF coil 6 based on a set pulse sequence (described later) transmitted from the computer system 10, and includes an oscillation unit, a phase selection unit, and a frequency conversion unit. An amplitude modulation unit, a high-frequency power amplification unit, and the like.

  The oscillation unit generates a high-frequency signal having a resonance frequency unique to the target nucleus in the static magnetic field. The phase selection unit selects the phase of the high-frequency signal. The frequency conversion unit converts the frequency of the high-frequency signal output from the phase selection unit. The amplitude modulation unit modulates the amplitude of the high-frequency signal output from the frequency modulation unit according to, for example, a sinc function. The high frequency power amplification unit amplifies the high frequency signal output from the amplitude modulation unit. As a result of the operation of each of these units, the transmission unit 7 transmits a high-frequency pulse corresponding to the Larmor frequency to the transmission RF coil 6.

  The reception RF coil 8 is a coil disposed inside the gradient magnetic field coil 2 and receives a magnetic resonance signal radiated from the subject due to the influence of the high-frequency magnetic field. When receiving the magnetic resonance signal, the reception RF coil 8 outputs the received magnetic resonance signal to the receiving unit 9.

  The receiving unit 9 generates magnetic resonance signal data by performing frequency conversion and A / D conversion of the magnetic resonance signal output from the reception RF coil 8 based on a set pulse sequence (described later) sent from the computer system 10. The generated magnetic resonance signal data is transmitted to the computer system 10.

  The computer system 10 is a device that performs overall control of the magnetic resonance imaging apparatus 100, data collection, image reconstruction, and the like. As shown in FIG. 1, an interface unit 11, a data collection unit 12, and a data processing unit. 13, a storage unit 14, a display unit 15, an input unit 16, and a control unit 17.

  The interface unit 11 is connected to the gradient magnetic field power source 3, the bed control unit 5, the transmission unit 7, and the reception unit 9, and inputs and outputs signals that are exchanged between these connected units and the computer system 10. A processing unit to be controlled.

  The data collection unit 12 collects the magnetic resonance signal data transmitted from the reception unit 9 via the interface unit 11, and arranges the collected magnetic resonance signal data in the k space to obtain k space data. It is. The data collection unit 12 stores the k-space data in the storage unit 14.

  The data processing unit 13 is a processing unit that reconstructs image data (magnetic resonance image) by performing post-processing, that is, reconstruction processing such as Fourier transform, on the k-space data stored in the storage unit 14.

  The storage unit 14 is a storage unit that stores, for each subject P, k-space data received from the data collection unit 12, magnetic resonance images reconstructed by the data processing unit 13, and the like.

  The display unit 15 is a monitor device such as a CRT (Cathode Ray Tube) display or a liquid crystal display that displays various information such as a magnetic resonance image under the control of the control unit 17.

  The input unit 16 receives various operations and information inputs from an operator, has a pointing device such as a mouse and a trackball, a keyboard, etc., and cooperates with the display unit 15 to provide a user interface for receiving various operations. Provided to the operator of the magnetic resonance imaging apparatus 100.

  The control unit 17 includes a CPU, a memory, and the like (not shown), and is a processing unit that comprehensively controls the magnetic resonance image diagnostic apparatus 100.

  Specifically, the control unit 17 includes various imaging parameters (slice position, slice direction, and the like based on a data collection method (for example, Spin Echo method, Fast Spin Echo method) input from the operator via the input unit 16. A pulse sequence is generated from the number of slices, slice thickness, repetition time, echo time, etc. Then, when an imaging start instruction is input from the operator via the input unit 16, the control unit 17 sets the generated pulse sequence as a set pulse sequence and uses the gradient magnetic field power source 3, the transmission unit 7, and the By transmitting to the receiving unit 9, the magnetic resonance image is captured.

  As described above, when the magnetic resonance image diagnostic apparatus 100 according to the present embodiment collects magnetic resonance signals generated from within the subject using the set pulse sequence and captures the magnetic resonance image, the control described in detail below. The main feature of the processing of the unit 17 is that it is possible to reliably capture a magnetic resonance image in which artifacts due to the movement of the subject are suppressed, and to improve the efficiency of image diagnosis. . This main feature will be described with reference to FIGS. Here, FIG. 2 is a functional block diagram showing a detailed configuration of the computer system in the present embodiment, FIG. 3 is a diagram for explaining a body motion correspondence sequence storage unit, and FIG. 4 is a sequence switching It is a figure for demonstrating a control part.

  Note that FIG. 2 shows a configuration particularly related to the present invention among the configurations of the control unit 17 and the storage unit 14, the interface unit 11, the data collection unit 12, the data processing unit 13, the storage unit 14, the control unit 17, the pressure The interrelationship of signals exchanged among the sensor 4b, the gradient magnetic field power source 3, the transmission unit 7, the reception unit 9, and the like is shown.

  As illustrated in FIG. 2, the storage unit 14 includes a body motion correspondence sequence storage unit 14 a, a collected data storage unit 14 b, and an image data storage unit 14 c.

  The collected data storage unit 14b stores the k-space data collected by the data collecting unit 12 and arranged in the k-space. The image data storage unit 14c stores a magnetic resonance image generated by the above-described data processing unit 13 through reconstruction processing.

  The body motion correspondence sequence storage unit 14a stores a body motion correspondence sequence referred to by a sequence switching control unit 17b described later for each imaging region. Here, when the set pulse sequence generated based on the imaging parameters input by the operator is a normal imaging sequence, the body motion correspondence sequence is a pulse sequence based on a data acquisition method having a shorter imaging time than the normal imaging sequence, or This is a pulse sequence based on a data acquisition method that can correct the movement of the examiner P.

  For example, as a body motion compatible sequence that can shorten the imaging time compared to the normal imaging sequence by collecting data at high speed, the gradient magnetic field between the phase encode gradient direction and the frequency encode gradient direction is increased at the time of magnetic resonance signal collection. One example is a pulse sequence based on the “Echo Planar Imaging method” that switches and fills the k-space like a stroke.

  In addition, as a body motion correspondence sequence that can shorten the imaging time by reducing the amount of data collection compared to the normal imaging sequence, the k-space is based on the property that uncollected magnetic resonance signals can be complemented by Hermitian symmetry. For example, a pulse sequence based on the “half Fourier method” of collecting magnetic resonance signals in which only half is filled. In addition, pulse sequences based on the Fast Field Echo method, the Spiral Fast Imaging method, and the like can also be cited as examples of the body motion compatible sequence that can shorten the imaging time.

  In addition, as a body movement correspondence sequence capable of detecting the movement of the subject P, a band-like region called “blade” formed by a plurality of parallel data collection trajectories is repeatedly rotated for each time period, so that A “blade rotation data collection sequence”, which is a pulse sequence based on a “blade rotation data collection method” that collects and fills k-space data in a non-orthogonal shape, can be mentioned.

  As described above, the body motion corresponding sequence is preset for each imaging region by the operator via the input unit 16 as a pulse sequence for corresponding to the body motion of the subject P, and the body motion corresponding sequence storage unit 14a. Stored in

  Thereby, for example, as shown in FIG. 3, the body movement corresponding sequence storage unit 14 a stores “A” as the body movement corresponding sequence when the imaging part is “head”, and the imaging part is “abdomen”. “B” is stored as a body motion correspondence sequence when the imaging region is “C”, and “C” is stored as a body motion correspondence sequence when the imaging region is “limb”, and the body when the imaging region is “pelvis” “D” is stored as the motion corresponding sequence. For example, the operator sets the “blade rotation data collection sequence” as “A” or “B”. Further, the operator sets a pulse sequence based on the above-described “Echo Planar Imaging method” as “C”, and sets a pulse sequence based on the above-described “half Fourier method” as “D”.

  In the present embodiment, the case where the body movement corresponding sequence is set for each imaging region has been described. However, the present invention is not limited to this, and in addition to the imaging region, the magnetic resonance image to be imaged can be captured. It may be a case where a body motion correspondence sequence is set in association with the type (T1-weighted image or T2-weighted image).

  Returning to FIG. 2, the control unit 17 includes a body movement determination unit 17a and a sequence switching control unit 17b.

  The body movement determination unit 17a sequentially receives the pressure applied to the top plate 4a from the pressure sensor 4b via the interface unit 11. The body movement determination unit 17a calculates the amount of pressure fluctuation every time pressure is received from the pressure sensor 4b. When the calculated amount of fluctuation exceeds a predetermined threshold, the body movement determination unit 17a Is determined to have occurred.

  The sequence switching control unit 17b executes the control described below when the body movement determination unit 17a determines that body movement has occurred in the subject P.

  First, the sequence switching control unit 17b is a first case in which it is determined by the body motion determination unit 17a that body motion has occurred in the subject P before the start of the main imaging by the normal imaging sequence set by the operator. Referring to the body motion correspondence sequence storage unit 14a, control is performed so as to switch from the normal imaging sequence to the body motion correspondence sequence corresponding to the imaging region of the subject P. Specifically, in the first case, the sequence switching control unit 17b refers to the body motion correspondence sequence storage unit 14a and generates a pulse sequence based on the body motion correspondence sequence corresponding to the imaging region of the subject P. The pulse sequence generated based on the body motion correspondence sequence is transmitted to the gradient magnetic field power source 3, the transmission unit 7, and the reception unit 9 via the interface unit 11 when the main imaging start instruction is received.

  In addition, before the start of the main imaging, after the subject P placed on the top 4a is moved into the cavity of the gradient magnetic field coil 2, "imaging the positioning image for imaging planning", "positioning This is a period from the input of imaging parameters with reference to an image and the generation of a set pulse sequence as a normal imaging sequence from the input imaging parameters until the main imaging start instruction is received from the operator.

  In addition, the sequence switching control unit 17b has already collected the magnetic resonance when the body movement determination unit 17a determines that body movement has occurred in the subject P during the main imaging in the normal imaging sequence as the set pulse sequence. Even in the second case where the data amount of the signal is smaller than the predetermined amount, the body motion correspondence sequence storage unit 14a is referred to switch from the normal imaging sequence to the body motion correspondence sequence corresponding to the imaging region of the subject P. To control.

  Specifically, the sequence switching control unit 17b refers to the collected data storage unit 14b that stores k-space data when body movement is detected in the subject P during the main imaging in the normal imaging sequence. As shown in (A) of 4, if the data collection amount is less than 80%, for example, the imaging in the normal imaging sequence is stopped, and the control is performed so that the imaging is switched to the body motion corresponding sequence and re-imaging is performed.

  In addition, the sequence switching control unit 17b has already collected the magnetic resonance when the body movement determination unit 17a determines that body movement has occurred in the subject P during the main imaging in the normal imaging sequence as the set pulse sequence. In the third case where the data amount of the signal is equal to or greater than the predetermined amount, the main imaging is stopped and the data processing unit 12 is controlled so as to reconstruct the magnetic resonance image only with the collected k-space data.

  Specifically, the sequence switching control unit 17b refers to the collected data storage unit 14b that stores k-space data when body movement is detected in the subject P during the main imaging in the normal imaging sequence. 4A, if the data collection amount is, for example, 80% or more, the gradient magnetic field power source 3, the transmission unit 7 and the reception unit 9 are connected via the interface unit 11 so as to stop imaging. In addition to the control, the data processing unit 12 is controlled so as to generate a magnetic resonance image by image reconstruction by a zero filling method in which the uncollected k-space region is filled with zero.

  When the k-space data is filled by the “blade rotation data collection sequence” as the set pulse sequence, the sequence switching control unit 17b performs the body movement of the subject P as shown in FIG. The data processing unit 12 is controlled so as to generate k-space data in which is canceled and to reconstruct the magnetic resonance image.

  Specifically, when the k-space data is filled by the “blade rotation data collection sequence”, the data processing unit 12 generates an image for each blade by Fourier transform based on the control of the sequence switching control unit 17b. Then, by comparing the generated images, the amount of movement between the images corresponding to each blade is determined. Then, the data processing unit 12 calculates a correction parameter for correcting the shift between the images by relative rotational movement or translational movement based on the determined movement amount. Then, the data processing unit 12 performs motion correction on each image based on the calculated correction parameter by rotational movement or translational movement, and performs inverse Fourier transform on each motion-corrected image, so that the body movement of the subject P is increased. Canceled k-space data is generated. And the data processing part 12 reconstructs the magnetic resonance image by which the artifact resulting from the motion of the subject P was suppressed by Fourier-transforming k-space data in which the body motion was canceled again.

  In addition, the sequence switching control unit 17b uses Hermite symmetry for uncollected magnetic resonance signals when the k-space data is filled by the pulse sequence based on the “half Fourier method” as the set pulse sequence. By performing the complement processing, the data processing unit 12 is controlled to reconstruct the magnetic resonance image.

  Next, processing of the magnetic resonance imaging apparatus in the present embodiment will be described using FIG. FIG. 5 is a flowchart for explaining processing of the magnetic resonance imaging apparatus according to the present embodiment.

  As shown in FIG. 5, in the magnetic resonance imaging apparatus 100 according to the present embodiment, when the subject P is moved to the inside of the static magnetic field magnet 1 by the bed control unit 15 according to an operator's instruction (step S501). Yes), the body movement determination unit 17a sequentially receives the pressure applied to the top 4a from the pressure sensor 4b via the interface unit 11, calculates the amount of pressure fluctuation, and calculates the calculated amount of fluctuation and a predetermined threshold value. To determine whether body movement has occurred in the subject P (step S502).

  Here, when it is not determined by the body movement determination unit 17a that body movement has occurred in the subject P (No in step S502), the control unit 17 gives an instruction to start main imaging via the input unit 16 from the operator. (Step S504). If the main imaging start instruction has not been received (No at step S504), the process returns to step S502, and the body movement determination process for the subject P is performed.

  On the other hand, when it is determined by the body movement determination unit 17a that body movement has occurred in the subject P (Yes in step S502, in the first case), the sequence switching control unit 17b refers to the body movement correspondence sequence storage unit 14a. Then, control is performed so as to switch from the normal imaging sequence to the body motion corresponding sequence corresponding to the imaging region of the subject P (step S503). That is, the sequence switching control unit 17b generates a pulse sequence based on the body motion corresponding sequence corresponding to the imaging region of the subject P, and sets the generated pulse sequence as the set pulse sequence.

  When the control unit 17 receives an instruction to start main imaging from the operator via the input unit 16 (Yes in step S504), the sequence switching control unit 17b sets the normal imaging sequence or the body motion corresponding sequence as a set pulse sequence. Is transmitted to the gradient magnetic field power source 3, the transmission unit 7, and the reception unit 9 through the interface unit 11 to start the main imaging based on the set pulse sequence (step S505).

  After that, the body motion determination unit 17a determines whether or not body motion has occurred in the subject P (step S506), as before the start of the main imaging, and the body motion has occurred in the subject P. If not (No at Step S506), the control unit 17 determines whether or not the collection of the k-space data has ended (Step S510).

  Here, when the collection of the k-space data is not completed (No at Step S510), the control unit 17 performs control so as to continue imaging with the set pulse sequence (Step S511), and returns to Step S506 to perform the test. The body motion determination unit 17a is controlled to perform the body motion determination process of the person P.

  On the other hand, when it is determined by the body motion determination unit 17a that body motion has occurred in the subject P (Yes in step S506), the sequence switching control unit 17b determines that the set pulse sequence is a body motion-compatible sequence (step S506). In S507, the control unit 17 determines whether or not the collection of the k-space data has ended (Step S510). Here, when the collection of the k-space data has not ended (No at Step S510), the control unit 17 performs control so as to continue the imaging by the body movement corresponding sequence (Step S511), and returns to Step S506 to The body motion determination unit 17a is controlled to perform the body motion determination process of the examiner P.

  If it is determined by the body motion determination unit 17a that body motion has occurred in the subject P (Yes at step S506), the sequence switching control unit 17b determines that the set pulse sequence is a normal imaging sequence (step S507). (Yes), it is determined whether or not the data collection amount of the k-space data is 80% or more (step S508).

  Here, when the data collection amount of the k-space data is less than 80% (No in step S508, in the second case), the sequence switching control unit 17b switches the set pulse sequence from the normal imaging sequence to the body motion-corresponding sequence. Then, it decides to re-image (step S509), returns to step S505, and controls to restart the main imaging based on the set pulse sequence (body motion correspondence sequence).

  On the other hand, when the data collection amount of the k-space data is 80% or more (Yes in step S508, in the third case), the sequence switching control unit 17b stops imaging and performs image reconstruction by the zero filling method. The data processing unit 13 is controlled (step S512), the data processing unit 13 performs image reconstruction by the zero filling method (step S513), and ends the process.

  If it is determined that the collection of k-space data has been completed as a result of the determination process in step S510 (Yes in step S510), the data processing unit 13 performs a normal imaging sequence based on the control by the sequence switching control unit 17b. Alternatively, image reconstruction is performed by a method corresponding to the body motion correspondence sequence (step S513), and the process is terminated.

  When a plurality of magnetic resonance images are taken for the same subject, the magnetic resonance imaging apparatus 100 in the present embodiment immediately before executing the image reconstruction process in step S513 (or the image reconstruction process). After the execution), the process returns to step S502, and the above-described series of processes is executed again from the body movement determination process of the subject P before imaging.

  As described above, in this embodiment, the body movement determination unit 17a sequentially receives the pressure applied to the top plate 4a from the pressure sensor 4b via the interface unit 11, and calculates the amount of pressure fluctuation. When the calculated fluctuation amount is equal to or greater than a predetermined threshold, it is determined that body movement has occurred in the subject P.

  In the first case, the sequence switching control unit 17b determines that the body motion has occurred in the subject P by the body motion determination unit 17a before the start of the main imaging by the normal imaging sequence set by the operator. Referring to the body motion correspondence sequence storage unit 14a, control is performed so as to switch from the normal imaging sequence to the body motion correspondence sequence corresponding to the imaging region of the subject P.

  In addition, the sequence switching control unit 17b refers to the collected data storage unit 14b when the body movement determination unit 17a determines that body movement has occurred in the subject P during the main imaging in the normal imaging sequence as the set pulse sequence. In the second case where the data amount of the magnetic resonance signals already collected is less than the predetermined amount, the body motion corresponding sequence corresponding to the imaging region of the subject P is referred to the body motion corresponding sequence storage unit 14a. Control is performed so that re-imaging is performed by switching from the normal imaging sequence.

  In addition, the sequence switching control unit 17b refers to the collected data storage unit 14b when the body movement determination unit 17a determines that body movement has occurred in the subject P during the main imaging in the normal imaging sequence as the set pulse sequence. In the third case where the data amount of the already collected magnetic resonance signal is equal to or greater than a predetermined amount, the main imaging is stopped, and the magnetic resonance image is reconstructed using only the collected k-space data. The processing unit 12 is controlled.

  Therefore, although the imaging time is increased only when the body motion correspondence sequence is the “blade rotation data collection sequence”, the main imaging is performed when only an insufficient amount of data is collected for image reconstruction. This is only in the second case where body movement occurs, and the number of re-imaging times can be reliably reduced due to the occurrence of body movement, resulting in the movement of the subject as described above. It is possible to improve the efficiency of image diagnosis by ensuring that a magnetic resonance image in which artifacts are suppressed is reliably captured.

  In addition, when body motion occurs in the subject P, the sequence is automatically switched to a body motion-compatible sequence, or if a sufficient amount of data is collected for image reconstruction, imaging is automatically stopped and image reconstruction is performed. Since the configuration can be executed, the burden on the operator can be reduced.

  In the above-described embodiment, the case has been described in which whether or not body movement has occurred in the subject P is determined based on the pressure acquired by the pressure sensor 4b attached to the top plate 4a. The present invention is not limited to this, and it may be a case where it is determined whether body movement has occurred in the subject P by the following four methods.

  The first method is a case where the operator visually observes the state of the subject P to determine whether body movement has occurred in the subject P. That is, when the operator visually determines that body movement has occurred in the subject P, for example, a body movement detection button installed on the input unit 16 is pressed.

  The second method generates a magnetic resonance image from k-space data of the same slice plane collected from the subject P at regular time intervals, and calculates the amount of variation in position information of a predetermined part in the generated magnetic resonance image. By doing so, it is a case where it is determined whether or not body movement has occurred in the subject P.

  For example, before the start of actual imaging, the pulse sequence is adjusted so that k-space data of the same slice plane is collected at regular time intervals when a positioning image for imaging planning is generated. The set pulse sequence is adjusted so that k-space data of the same slice plane is collected at each interval.

  Thereby, the data processing unit 13 reconstructs a magnetic resonance image along the time series of the same slice plane of the subject P, and the body motion determination unit 17a extracts a predetermined part of the magnetic resonance image, A fluctuation amount of the coordinates of the predetermined part is calculated. For example, the body motion determination unit 17a extracts a head contour, an eyeball, and the like from a magnetic resonance image obtained by imaging the head, and calculates a variation amount (motion vector) along the time series of these coordinates. And the body movement determination part 17a determines with the body movement having generate | occur | produced in the subject P, when the calculated fluctuation amount becomes more than a predetermined threshold value.

  The third method is to collect a magnetic resonance signal called navigator echo from the peripheral region of the diaphragm separately from the magnetic resonance signal for imaging when imaging a part including the diaphragm of the subject P. This is a case where it is determined whether or not body movement has occurred in the subject P. That is, the body motion determination unit 17a identifies the position of the diaphragm by creating one-dimensional data around the diaphragm from the navigator echo, and the periodic fluctuation amount of the identified diaphragm position deviates from a predetermined threshold value It is determined that body movement has occurred in the subject P.

  In the fourth method, profile data is generated from magnetic resonance signal data of the same slice plane collected from the subject P at regular time intervals, and the amount of change in position information of a predetermined part in the generated profile data is calculated. Thus, it is a case where it is determined whether or not body movement has occurred in the subject P. Hereinafter, the fourth method will be described with reference to FIGS. 6 to 10 are diagrams for explaining the fourth method.

  First, the sequence switching control unit 17b executes imaging for body motion profile data for collecting profile data in order to determine whether or not body motion has occurred during imaging of a magnetic resonance image. At this time, in order to accurately determine the presence / absence of body movement, the sequence switching control unit 17b captures body motion profile data so as to collect profile data of slice planes in the same part as the part of the magnetic resonance image. Is executed. Further, the sequence switching control unit 17b executes imaging for body motion profile data so that the slice plane includes the magnetic field center. When imaging a magnetic resonance image, the imaging region of the subject P is usually moved to the center of the magnetic field that is the center of the static magnetic field generated by the static magnetic field magnet 1 in order to capture a high-quality magnetic resonance image. Therefore, profile data with a high S / N ratio of signal intensity can be collected by controlling the slice surface at the time of imaging for body motion profile data to include the magnetic field center.

  For example, as shown in FIG. 6, the sequence switching control unit 17b sets the slice plane for collecting profile data to the head when the imaging part of the magnetic resonance image is the head of the subject P, and The slice plane for collecting profile data is set so as to include the center of the magnetic field, and imaging for body motion profile data is executed.

  Furthermore, as shown in FIG. 7, the sequence switching control unit 17b repeatedly executes body motion profile data imaging at regular time intervals during imaging of a nuclear magnetic resonance image. For example, the sequence switching control unit 17b performs control so that imaging for body motion profile data is executed every 60 seconds. Alternatively, the sequence switching control unit 17b performs control so that the sequence switching control unit 17b is executed each time the repetition time set in the image imaging pulse sequence elapses.

  The data processing unit 13 that has received the magnetic resonance signal data collected by the imaging for body motion profile data generates profile data by performing first-order Fourier transform on the received magnetic resonance signal data. Then, the body motion determination unit 17a calculates the variation amount of the profile data generated sequentially. For example, as shown in FIG. 8, the body movement determination unit 17a detects a signal intensity detection position where the signal intensity is maximum every time profile data is generated, and calculates a variation amount of the detected signal intensity detection position. To do. And the body movement determination part 17a determines with the body movement having generate | occur | produced in the subject P, for example, when the calculated fluctuation amount becomes more than the preset threshold value.

  Here, in the fourth method, body motion determination may be performed using a table in which imaging intervals and threshold values for imaging of body motion profile data are set for each imaging region of the nuclear magnetic resonance image. For example, as illustrated in FIG. 9, when a table in which “imaging interval: 60 seconds” and “threshold value: 5 mm” are associated with “imaging region: head” is stored, the sequence switching control unit 17b controls so that imaging for body motion profile data is executed every 60 seconds during the imaging of the head, and the body motion determination unit 17a determines that the calculated fluctuation amount is 5 mm or more. It is determined that body movement has occurred in the subject P.

  Note that the threshold shown in FIG. 9 is set to an arbitrary value by the operator of the magnetic resonance imaging apparatus 100 according to the imaging region. For example, when the imaging region is the head, the operator sets the threshold value to a small value because it wants to reduce the magnetic resonance image artifacts caused by the body movement of the subject P as much as possible. Further, when the imaging region is a small region such as the lower limb or the upper limb, the influence of the body movement of the subject P becomes large, and therefore the operator sets the threshold value to a small value. That is, by setting a table as shown in FIG. 9, it is possible to perform body movement determination according to the imaging region.

  Then, when it is determined that body movement has occurred in the subject P by the above-described four methods, the sequence switching control unit 17b is normal if it is before the main imaging as in the above-described embodiment. If the set pulse sequence is switched from the imaging sequence to the body motion-corresponding sequence and the main imaging is being performed, a set pulse sequence switching process or an imaging stop process based on the collection amount of k-space data is executed.

  As described above, the magnetic resonance imaging apparatus and the magnetic resonance imaging method according to the present invention are useful when imaging magnetic resonance images by collecting magnetic resonance signals from within the subject using a predetermined data collection method. In particular, it is suitable for improving the efficiency of image diagnosis by ensuring that a magnetic resonance image in which artifacts due to the movement of the subject are suppressed is reliably captured.

DESCRIPTION OF SYMBOLS 1 Static magnetic field magnet 2 Gradient magnetic field coil 3 Gradient magnetic field power supply 4 Bed 4a Top plate 4b Pressure sensor 5 Bed control part 6 Transmission RF coil 7 Transmission part 8 Reception RF coil 9 Reception part 10 Computer system 11 Interface part 12 Data collection part 13 Data Processing unit 14 Storage unit 14a Body motion correspondence sequence storage unit 14b Collected data storage unit 14c Image data storage unit 15 Display unit 16 Input unit 17 Control unit 17a Body motion determination unit 17b Sequence switching control unit 100 Magnetic resonance image diagnostic apparatus

Claims (19)

The magnetic resonance signals from within the subject are collected by a predetermined data collection method and controlled to take a magnetic resonance image, and when the subject's movement is detected, the predetermined data collection method The magnetic resonance signal is collected by switching to a data collection method having a shorter imaging time than the predetermined data collection method or a second data collection method which is a data collection method capable of correcting the movement of the subject. A data collection control unit for controlling
An image reconstruction unit for reconstructing the magnetic resonance image from the magnetic resonance signals collected based on the data collection method executed under the control of the data collection control unit;
A magnetic resonance imaging apparatus comprising:   The data collection control unit is already collected in the first case where the movement of the subject is detected before imaging and when the movement of the subject is detected during imaging by the predetermined data collection method. In the second case where the data amount of the magnetic resonance signal is smaller than a predetermined amount, control is performed so as to switch from the predetermined data acquisition method to the second data acquisition method for imaging, and according to the predetermined data acquisition method. In the third case where the data amount of the magnetic resonance signal already collected at the time when the subject's movement is detected during imaging, the imaging is stopped and the collected magnetic resonance signal The magnetic resonance imaging apparatus according to claim 1, wherein the image reconstruction unit is controlled so as to reconstruct the magnetic resonance image only by itself.   The data collection control unit detects movement of the subject from a fluctuation amount of pressure applied to the top plate acquired from a pressure sensor attached to the top plate on which the subject is placed. 2. The magnetic resonance imaging apparatus according to 2.   3. The magnetism according to claim 2, wherein the data collection control unit detects the movement of the subject from a variation amount of position information of the predetermined part based on a magnetic resonance signal in the predetermined part in the subject. Resonance diagnostic imaging device. A second data collection method storage unit that stores the second data collection method in association with the imaging site and / or the type of magnetic resonance image;
In the first case and the second case, the data collection control unit is configured to associate the second region associated with the imaging region and / or the magnetic resonance image type in which the subject is actually imaged. The magnetic resonance imaging apparatus according to claim 2, wherein the data collection method is acquired from the second data collection method storage unit. A second data collection method storage unit that stores the second data collection method in association with the imaging site and / or the type of magnetic resonance image;
In the first case and the second case, the data collection control unit is configured to associate the second region associated with the imaging region and / or the magnetic resonance image type in which the subject is actually imaged. The magnetic resonance imaging apparatus according to claim 3, wherein a data collection method is acquired from the second data collection method storage unit. A second data collection method storage unit that stores the second data collection method in association with the imaging site and / or the type of magnetic resonance image;
In the first case and the second case, the data collection control unit is configured to associate the second region associated with the imaging region and / or the magnetic resonance image type in which the subject is actually imaged. The magnetic resonance imaging apparatus according to claim 4, wherein a data collection method is acquired from the second data collection method storage unit. The second data collection method is a data collection method for collecting the magnetic resonance signals by repeatedly rotating a band-like region formed by a plurality of parallel data collection trajectories in a frequency space at every time,
The image reconstruction unit reconstructs the magnetic resonance image based on a correction parameter for correcting the movement of the subject detected from the magnetic resonance signal collected by the second data collection method. Item 3. The magnetic resonance imaging apparatus according to Item 2. The second data collection method is a data collection method for collecting the magnetic resonance signals by repeatedly rotating a band-like region formed by a plurality of parallel data collection trajectories in a frequency space at every time,
The image reconstruction unit reconstructs the magnetic resonance image based on a correction parameter for correcting the movement of the subject detected from the magnetic resonance signal collected by the second data collection method. Item 4. The magnetic resonance imaging apparatus according to Item 3. The second data collection method is a data collection method for collecting the magnetic resonance signals by repeatedly rotating a band-like region formed by a plurality of parallel data collection trajectories in a frequency space at every time,
The image reconstruction unit reconstructs the magnetic resonance image based on a correction parameter for correcting the movement of the subject detected from the magnetic resonance signal collected by the second data collection method. Item 5. The magnetic resonance imaging apparatus according to Item 4. The second data collection method is a data collection method for collecting the magnetic resonance signals by repeatedly rotating a band-like region formed by a plurality of parallel data collection trajectories in a frequency space at every time,
The image reconstruction unit reconstructs the magnetic resonance image based on a correction parameter for correcting the movement of the subject detected from the magnetic resonance signal collected by the second data collection method. Item 6. The magnetic resonance imaging apparatus according to Item 5. The second data collection method is a data collection method for collecting the magnetic resonance signals by repeatedly rotating a band-like region formed by a plurality of parallel data collection trajectories in a frequency space at every time,
The image reconstruction unit reconstructs the magnetic resonance image based on a correction parameter for correcting the movement of the subject detected from the magnetic resonance signal collected by the second data collection method. Item 7. The magnetic resonance imaging apparatus according to Item 6. The second data collection method is a data collection method for collecting the magnetic resonance signals by repeatedly rotating a band-like region formed by a plurality of parallel data collection trajectories in a frequency space at every time,
The image reconstruction unit reconstructs the magnetic resonance image based on a correction parameter for correcting the movement of the subject detected from the magnetic resonance signal collected by the second data collection method. Item 8. The magnetic resonance imaging apparatus according to Item 7.   The data collection control unit detects a movement of the subject from a variation amount of position information of the predetermined part calculated from profile data based on a magnetic resonance signal at a predetermined part in the subject. Item 5. The magnetic resonance imaging apparatus according to Item 4.   The magnetic resonance imaging apparatus according to claim 14, wherein the data collection control unit controls the predetermined part to be the same as an imaging part of the nuclear magnetic resonance image.   The magnetic resonance imaging apparatus according to claim 15, wherein the data collection control unit controls the predetermined part to include a magnetic field center in an imaging part of the nuclear magnetic resonance image.   17. The magnetic resonance according to claim 16, wherein the data collection control unit performs control so that imaging for collecting the profile data is repeatedly executed at predetermined time intervals during imaging of the nuclear magnetic resonance image. Diagnostic imaging device. A threshold storage unit for storing a predetermined time interval set for each imaging region of the nuclear magnetic resonance image and a predetermined threshold;
The data collection control unit acquires a predetermined time interval and a predetermined threshold associated with the imaging site of the nuclear magnetic resonance image from the threshold storage unit, and acquires the profile data at the acquired predetermined time interval. Control is performed so as to perform imaging for collection, and the amount of change in the positional information of the predetermined part calculated from the profile data collected by the imaging performed at the predetermined time interval and the acquired predetermined 18. The magnetic resonance imaging apparatus according to claim 17, wherein control is performed so as to determine the presence or absence of movement of the subject by comparing with a threshold value. The magnetic resonance signals from within the subject are collected by a predetermined data collection method and controlled to take a magnetic resonance image, and when the subject's movement is detected, the predetermined data collection method The magnetic resonance signal is collected by switching to a data collection method having a shorter imaging time than the predetermined data collection method or a second data collection method which is a data collection method capable of correcting the movement of the subject. A data collection control step for controlling
An image reconstruction step of reconstructing the magnetic resonance image from the magnetic resonance signal acquired based on the data acquisition method executed by the control of the data acquisition control step;
A magnetic resonance imaging method including:

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